3-[(3R,4R)-4-Methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]piperidin-1-yl]-3-oxopropionitrile (Formula 1), commonly known as tofacitinib, is disclosed in WO 01/42246 A1 and WO 02/096909 A1. XELJANZ™ a commercial form of the citrate salt of tofacitinib, is indicated for the treatment of adult patients with moderately to severely active rheumatoid arthritis who have had an inadequate response or intolerance to methotrexate.

WO 03/048162 A1 relates to a novel amorphous and crystalline forms of 3-{(3R,4R)-4-methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]-piperidin-1-yl}-3-oxo-propionitrile mono-citrate salt, useful as inhibitors of protein kinases, and to their methods of preparation.
WO 2012/135338 A1 is directed to tofacitinib acid addition salts and solid state forms thereof, particularly amorphous tofacitinib acetate, as well as pharmaceutical compositions comprising one or more of them. The invention further provides a process for producing tofacitinib acid addition salt, in particular, tofacitinib mono-citrate salt.
WO 2012/137111 A1 discloses novel crystalline and non-crystalline forms of 3-((3R,4R)-4-methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]-piperidin-1-yl)-3-oxopropionitrile, pharmaceutical composition containing the same, preparations thereof and the uses thereof.
WO 2013/090490 A1 is directed to several tofacitinib salts including tofacitinib mono-tartrate salt, tofacitinib mono-malate salt and tofacitinib mono-oxalate salt. These tofacitinib salts can be in amorphous form. The invention is also directed toward a pharmaceutical composition comprising one or more of the tofacitinib salts, and a process for preparing the composition. The tofacitinib salts can be used to prepare tofacitinib mono-citrate salt. Another aspect of the invention is a process for preparing tofacitinib mono-citrate. The tofacitinib salts of the invention are also useful as medicaments and in methods of treating patients suffering from cancer.
CN 103073552 A provides a preparation method for amorphous tofacitinib citrate. The preparation method is simple, can easily obtain high-purity amorphous tofacitinib citrate, and is suitable for industrial application. The preparation method includes the following steps: under the temperature range between 30° C. and 50° C., organic solvent is used for dissolving tofacitinib citrate, so that solution is produced, water which is 15° C. to 25° C. is added into the solution, so that precipitate is produced, the precipitate is put in the environment of 15° C. to 25° C. for 4 to 24 hours, and the amorphous tofacitinib citrate is then recovered.